The purpose of this study is to investigate the impact of pre- and postnatal exposure to cigarettes and associated risk factors on infant regulation. Regulation during infancy is defined by the ability to modulate autonomic processes by maintaining physiological homeostasis as well as the ability to modulate responsiveness to both nonsocial and social stimuli. Difficulties with these regulatory processes may interfere with attentional processes and the infant's ability to successfully cope with sensory challenges from the external environment. While several studies have indicated that prenatal exposure to cigarettes is associated with altered regulatory functioning in neonates, it is unclear whether these effects persist beyond the neonatal period. Furthermore, the impact that postnatal exposure to cigarette smoke has on regulatory processes has received almost no attention. This study will examine the possibility that early exposure to cigarettes may impact regulation beyond the neonatal period through several pathways. The first is the direct teratological impact of prenatal cigarette exposure on regulatory processes. The second potential pathway is the impact of exposure to environmental cigarette smoke (passive smoking) on regulatory processes. A third pathway may be through the impact of maternal cigarette use on growth outcomes that, in turn, influence infant reactivity and regulation. The protocol consists of examining mother-infant dyads at 2 weeks of age and again at 7 months of infant age. The final sample will consist of 60 infants who were prenatally exposed to cigarettes, 60 infants who were passively exposed to cigarette smoke and 60 infants who were not exposed to cigarettes either prenatally or postnatally. Assessments of physiological (vagal tone) and behavioral reactivity and regulation will be conducted at both assessment points. In addition, mother-infant interactions and the quality of the caregiving environment (quality of home environment and maternal psychopathology) will be assessed. The study will provide information about potential teratogenic effects of cigarette exposure on regulatory processes. It will also allow a preliminary examination of potential pathways to dysregulation. Such knowledge may have significant implications for prevention programs designed to ameliorate regulatory disturbances among children exposed to cigarettes.